<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        canvas {
            background-color: black;
        }

        body {
            margin: 0px;
        }
    </style>
</head>

<body>
    <canvas></canvas>
    <script>
        var canvas = document.querySelector('canvas')
        var ctx = canvas.getContext('2d')
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        var arr = ['red', 'blue', 'pink', 'orange', 'yellow']
        //面向对象编程
        //构造器函数->生产对象
        function Demo() {
            this.x = Math.random() * window.innerWidth;
            this.y = Math.random() * window.innerHeight;
            this.r = Math.random() * 15 + 5;
            this.color = arr[Math.floor(Math.random() * 5)]
        }
        var arr1 = []
        for (var i = 0; i < 100; i++) {
            arr1.push(new Demo())
        }
        for (var j = 0; j < arr1.length; j++) {
            ctx.beginPath() //落笔
            ctx.arc(arr1[j].x, arr1[j].y, arr1[j].r, 0, Math.PI * 2)  //x y 半径 起始角度 终止角度
            ctx.strokeStyle = arr1[j].color
            ctx.stroke()
            ctx.closePath() //提笔
        }






    </script>
</body>

</html>